实验研究了蓝色飞秒激光(1 kHz, 50 fs, 400 nm)在105 Pa(标准气压)和10－3 Pa两种不同气压环境下, 在单晶硅衬底的金属铬膜表面形成亚波长(~250 nm)一维周期性条纹结构的情况, 分析比较了入射激光能流、样品扫描速度、样品薄膜厚度等参数对表面条纹结构的影响.结果表明, 10－3 Pa的真空环境可以有效改善铬膜表面亚波长条纹结构的形成质量; 随着铬膜厚度的减小(100 ~25 nm),表面条纹质量逐渐提高, 但当铬膜太薄(≤ 25 nm)时材料表面易出现烧蚀不均匀现象; 另外, 随着飞秒激光能流密度的降低或扫描速度的增大, 条纹结构的空间周期将会减小, 此时条纹之间的沟槽内逐渐出现纳米线分布.

The formation of one dimensional periodic subwavelength (~250 nm) ripple structures on the surface of Si-based Cr film was investigated by irradiation of blue femtosecond laser pulses (1 kHz, 50 fs, 400 nm) under different ambient air pressures of 105 Pa (or 1atm) and 10－3 Pa. The effects of the experimental parameters such as the incident laser energy fluence, the sample scanning speed and the film thickness, on the development of the surface ripple structures were compared. The results demonstrate that the quality of the surface structures can be effectively improved either by the low air pressure of 10－3 Pa or by reducing the thickness of Cr film (100 ~25 nm), however, the uneven ablation may be appeared when the Cr film is too thin (≤ 25 nm). Moreover, with decreasing the laser energy fluence or increasing the scanning speed, the spatial period of the ripple structures tends to become smaller, accompanied by the nanowires growth inside the grooves of the ripple structures.